M&S is gearing up to take on the big four with a significant move towards becoming a one-stop-shop.

It has brought out a comprehensive cooking ingredients range and said this week it was taking a "serious" look at introducing major food brands such as Marmite to compete better.

The 150-strong ingredients range, which was launched this month and will grow to 300 by June, is a major step towards M&S repositioning itself as a one-stop grocery shop, following its recent reclassification by the Competition Commission.

"This is a totally new departure for us," said director of food Steven Esom. "From now on customers looking to cook from scratch and wanting to buy all their ingredients under one roof will increasingly find all they need at M&S."

M&S chief executive Stuart Rose said the range's launch was an important part of the strategy to boost food sales, which fell 1.5% like-for-like in the 13 weeks to 29 December. "The old M&S would have said you're lucky to come into our shop," Rose told The Grocer. "But we realise we must give customers what they want to stop them going across the road to buy it."

Rose said he would consider introducing branded goods, such as Marmite, in 2008 in order to compete more effectively. "We introduced televisions last year and they had a good time at Christmas," he said. "We are reviewing constantly."

The ingredients range, which was a year in development, is split into four categories - 'Cook With', 'Serve With', 'Flavour With' and 'Bake With' - designed to make it easy for customers to find the right ingredient.

'Cook With' features stocks, organic beans & pulses and wet & dry spice mixes. 'Serve With' includes 17 different rices, grains and noodles, many organic. A range of seasonings, oils, vinegars and sauces feature in 'Flavour With', while 'Bake With' includes bread, cookie and cake mixes, ready-to-roll icing and marzipan and a selection of organic dried fruits, nuts and seeds.

The entire range is free from artificial colours and flavourings.